Happy end

src/InsuranceCalculator.java

@@ -1,15 +1,24 @@
+import java.lang.Math;
+
 public class InsuranceCalculator {
 
+    private InsuranceStrategy strategy;
+
     public double calculateInsurance(double income) {
-        if (income <= 10000) {
-            return income*0.365;
-        } else if (income <= 30000) {
-            return (income-10000)*0.2+35600;
-        } else if (income <= 60000) {
-            return (income-30000)*0.1+76500;
-        } else {
-            return (income-60000)*0.02+105600;
+        InsuranceStrategy[] hashBrown = new InsuranceStrategy[6];
+        hashBrown[0] = new InsuranceStrategyLow();
+        hashBrown[1] = new InsuranceStrategyMedium();
+        hashBrown[2] = new InsuranceStrategyMedium();
+        hashBrown[3] = new InsuranceStrategyHigh();
+        hashBrown[4] = new InsuranceStrategyHigh();
+        hashBrown[5] = new InsuranceStrategyHigh();
+        int deviousNum = (int)Math.floor(Math.abs(income / 10000 - 0.1));
+        try {
+            strategy = hashBrown[deviousNum];
+            return strategy.calculate(income);
+        } catch(ArrayIndexOutOfBoundsException error) {
+            strategy = new InsuranceStrategyVeryHigh();
+            return strategy.calculate(income);
         }
     }
-
 }

src/InsuranceStrategy.java

@@ -0,0 +1,11 @@
+public abstract class InsuranceStrategy {
+    public double calculate(double income) {
+        return (income - getAdjustment()) * getWeight() + getConstant();
+    }
+
+    public abstract int getConstant();
+
+    public abstract double getWeight();
+
+    public abstract int getAdjustment();
+}

src/InsuranceStrategyHigh.java

@@ -0,0 +1,16 @@
+public class InsuranceStrategyHigh extends InsuranceStrategy {
+    @Override
+    public int getConstant() {
+        return 76500;
+    }
+
+    @Override
+    public double getWeight() {
+        return 0.1;
+    }
+
+    @Override
+    public int getAdjustment() {
+        return 30000;
+    }
+}

src/InsuranceStrategyLow.java

@@ -0,0 +1,16 @@
+public class InsuranceStrategyLow extends InsuranceStrategy {
+    @Override
+    public int getConstant() {
+        return 0;
+    }
+
+    @Override
+    public double getWeight() {
+        return 0.365;
+    }
+
+    @Override
+    public int getAdjustment() {
+        return 0;
+    }
+}

src/InsuranceStrategyMedium.java

@@ -0,0 +1,16 @@
+public class InsuranceStrategyMedium extends InsuranceStrategy {
+    @Override
+    public int getConstant() {
+        return 35600;
+    }
+
+    @Override
+    public double getWeight() {
+        return 0.2;
+    }
+
+    @Override
+    public int getAdjustment() {
+        return 10000;
+    }
+}

src/InsuranceStrategyVeryHigh.java

@@ -0,0 +1,16 @@
+public class InsuranceStrategyVeryHigh extends InsuranceStrategy {
+    @Override
+    public int getConstant() {
+        return 105600;
+    }
+
+    @Override
+    public double getWeight() {
+        return 0.02;
+    }
+
+    @Override
+    public int getAdjustment() {
+        return 60000;
+    }
+}

test/InsuranceCalculatorTest.java

@@ -0,0 +1,44 @@
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class InsuranceCalculatorTest {
+    @Test
+    public void low() {
+        assertEquals(
+                1825,
+                insuranceFor(5000),
+                0.01
+        );
+    }
+
+    @Test
+    public void medium() {
+        assertEquals(
+                38600,
+                insuranceFor(25000),
+                0.01
+        );
+    }
+
+    @Test
+    public void high() {
+        assertEquals(
+                78500,
+                insuranceFor(50000),
+                0.01
+        );
+    }
+
+    @Test
+    public void veryHigh() {
+        assertEquals(
+                106400,
+                insuranceFor(100000),
+                0.01
+        );
+    }
+
+    private double insuranceFor(double income) {
+        return new InsuranceCalculator().calculateInsurance(income);
+    }
+}